Fuel injection pump for diesel engines

Abstract

A fuel injection pump for diesel engines, in which the pressure chamber of each cylinder (10) is defined on its side opposite the piston (16) by a slide valve (38) movable in a direction opposite the piston against the action of resilient biasing means (52). The slide valve is sensitive to the supply pressure of the fuel and controls communication between the pressure chamber and the fuel delivery passage (44, 46). The supply pressure is controlled by external modulating means which varies the equilibrium position of the slide valve. The slide valve allows the initial alteration of the effective delivery, and hence the effective injection advance, in dependence on the running conditions/load of the engine.

We claim: 
     
       1. A fuel injection pump for diesel engines, including: at least one cylinder defining a pressure chamber, a radial fuel intake opening communicating with the pressure chamber, a delivery passage for the pumped fuel which is connectible to the pressure chamber, and a fuel return opening;   a piston which is sealingly and reciprocatingly slidable in the cylinder and arranged to cut off communication between the pressure chamber and the fuel intake opening during its pumping stroke, the piston being rotatable in the cylinder and having a helical groove in its lateral surface and an axial hole which communicates with the groove and opens into the pressure chamber, said groove also cooperating with the fuel return opening to regulate the delivery by means of rotational movements of the piston, and   an external regulating member for effecting rotatable movements of the piston,   wherein the improvement consists in a slide valve and an associated resilient biasing member being inserted in the cylinder, the slide valve defining a side of the pressure chamber opposite the piston and controlling the communication between the pressure chamber and the fuel delivery passage, the slide valve being movable from an initial equilibrium position in the direction of a pumping movement of the piston against the action of the resilient biasing member,   wherein said initial equilibrium position of the slide valve is dependent on the supply pressure of the fuel and external modulating means is provided for modulating the supply pressure so as to vary the initial equilibrium position of the slide valve.   
     
     
       2. Fuel injection pump as defined in claim 1, wherein the slide valve defines internal passages and is inserted in a tubular connector fitted to the top of the cylinder, said connector having an internal circumferential groove which communicates with the delivery passage and can communicate with the pressure chamber through the internal passages in the slide valve at the end of the travel of the latter against the action of said resilient biasing member.